A group of Senate Democrats is calling for an expanded investigation into efforts by the Trump Environmental Protection Agency to effectively push independent scientists off key EPA advisory boards and replace them with scientists from the fossil fuel and chemical industries.

In a letter sent to the Government Accountability Office on Thursday, the 10 senators asked the GAO to investigate a new directive, issued by EPA Administrator Scott Pruitt on Oct. 31, that restricts any scientist who has received EPA funding from serving on the agency’s scientific advisory panels.

Pruitt said the move was intended to clear up conflicts of interest and to rid advisory panel members of financial ties to the agency. But scientific groups, academics and advocacy organizations have all pointed out that it will mean the most experienced scientists—whose qualifications earn them government grants in the first place—will no longer be able to serve in these roles.

“The double-standard is striking: an academic scientist that receives an EPA grant for any purpose cannot provide independent advice on a completely different subject matter on any of EPA’s science advisory boards,” the senators wrote, “while industry scientists are presumed to have no inherent conflict even if their research is entirely funded by a company with a financial stake in an advisory board’s conclusions.”

Five days after Pruitt issued the directive, The Washington Post reported that he appointed 66 new members to advisory panels, many of them with ties to industries the agency regulates. Several panel members stepped down.

“Under this new policy, EPA will be replacing representatives of public and private universities including Harvard, Stanford, Ohio State University, and the University of Southern California with scientists who work for Phillips 66, Total, Southern Company, and the American Chemistry Council,” the senators wrote.

In response to a request for comment, an EPA spokesperson replied: “The Administrator has issued a directive which clearly states his policy with regard to grantees.” The agency did not respond to questions about whether new members will be required to sign conflict of interest declarations or undergo a review process.

Earlier this year, the EPA said it would not renew the terms of members of its broader Board of Scientific Counselors, and beyond EPA, the administration has allowed other scientific boards to expire altogether. In August, the acting head of the National Oceanic and Atmospheric Administration (NOAA) told members of an advisory panel for the National Climate Assessment that it would allow the panel’s charter to lapse.

The recent Pruitt directive is similar to legislation long pushed by Republicans in Congress, including a bill introduced earlier this year called the EPA Science Advisory Board Reform Act.

Science organizations have pointed out that anyone receiving a federal grant undergoes a merit review, which scrutinizes their professional standards and ethics, and that grant applicants have to declare they have no conflicts of interest before receiving government grants.

“EPA’s decisions have real implications for the health and well-being of Americans and in some cases people worldwide,” wrote Chris McEntee, the executive director of the American Geophysical Union. “By curtailing the input of some of the most respected minds in science, Pruitt’s decision robs the agency, and by extension Americans, of a critically important resource.”

The senators’ letter on Thursday follows a previous request to the GAO, the investigative arm of Congress, to investigate the EPA’s policies and procedures related to advisory panels.